1. Field of the Invention.
The present invention is related to a fluid powered downhole vibration tool which will be used in a subterranean well bore having fluids under pressure. In particular, the present invention is directed to a fluid powered downhole vibration tool powered by fluid flow from the formation itself in order to drive a seismic source.
2. Prior Art.
The concept of generating a vibrational signal underground which is used for seismic purposes is known. The vibrational signal may be used for a variety of purposes, such as in gas wells where condensation has built up in the formation near the well bore and has been limiting production. Vibrational energy from a downhole seismic source would improve the mobility of the fluids trapped in the formation and, therefore, increase well productivity.
An underground vibrational signal can also be used to allow investigation of subterranean structures. The downhole vibrational signal is used as a seismic energy source for generating information as to geology surrounding the borehole.
The seismic signals radiate in the earth. Much information can be procured at the earth's surface or in adjacent boreholes as to the rate of travel and the reflection of seismic signals. Upon analysis of the receipt of the seismic signals, much can be learned about the structure of the earth surrounding the borehole and the structure of the earth in the area between the borehole and the point where the seismic signals are generated and the earth's surface or the adjacent well bore. Analysis of the received signals resulting from the seismic signals can be carried out at the site or remotely. The seismic source has many applications. For example, the seismic signal makes it possible to more effectively obtain critical seismic profiles of the earth surrounding a borehole. Improved crosswell tomography geophysical techniques can be practiced using the high energy vibrational source.
Many types of cementing and production enhancement techniques can be improved when combined with downhole vibrational energy sources. As an example, cementing and gravel packing can be improved with the use of downhole vibrational energy source.
The use of vibrational energy in a subterranean borehole is shown in Applicant's prior patents, such as U.S. Pat. No. 5,159,160; U.S. Pat. No. 5,309,405; U.S. Pat. No. 5,210,381; and U.S. Pat. No. 5,515,918, which spin a shaft to create rotational energy which is used to create vibrational energy in the borehole. Each of these is incorporated herein by reference. In Applicant's prior disclosures, however, an energy source from the surface is used, such as an electric, hydraulic or mechanical motor.
By having the well bore fluids power the vibrational source, cost could be reduced compared with having a power source at the surface.
Accordingly, it is a principal object and purpose of the present invention to provide a downhole vibrational tool which is primarily powered by produced fluids under pressure in the well bore.
Fluid powered motors are also known. Fluid powered motors accept fluid power and convert it into mechanical power output. Various types of fluid powered motors are known. For example, the motors known as Moineau motors. Examples are shown in Moineau (U.S. Pat. No. 2,085,115; 1,892,217 and 2,483,370). In these motors, at least a pair of helical members, disposed one within the other, includes an inner member having an exterior that is constantly in contact with an outer member. At least one of the gears is rotatable about the longitudinal axis. Other types of fluid powered motors include gear type motors, rotary vane motors and reciprocating motors.
It is a further object and purpose of the present invention to provide a downhole vibrational tool having a fluid powered motor which rotates a seismic source within the well bore.
It is an additional object and purpose of the present invention to provide a downhole vibrational tool for generating vibration in a well bore wherein the vibrational energy may be controlled and regulated.
It is an additional object and purpose of the present invention to provide a downhole vibrational tool having a fluid powered motor with at least a pair of helical members disposed one within the other, each rotatable about a longitudinal axis.
It is also known to utilize a fluid oscillator within a subterranean well bore. Examples include Galle et al. (U.S. Pat. No. 3,405,770), Bodine (U.S. Pat. No. 4,702,315), Fast et al. (U.S. Pat. No. 3,743,017) and Barnard (U.S. Pat. No. 4,775,016).
It would be desirable to power a fluid oscillator with the differential pressure of the fluid in the subterranean well bore. Accordingly, it is another object and purpose of the present invention to provide a downhole vibrational tool having a fluid oscillator within the well bore which engages the well bore to cause vibration of the well bore.